In addition, there were indications that some customers continue to have e-mail problems, although the company says the feature has been restored since the outage.
The Instant Messenger bug, brought to AOL's attention by a subscriber, would allow a user to send crash-inducing computer code to members they are chatting with.
Fix expected quickly
"We're working to resolve the problem and we should have a fix fairly quickly," said AOL spokeswoman Wendy Goldberg. She declined to estimate how long it might take to deliver a fix.
Reports that the bug enables users to send viruses to other users are not true, Goldberg added.
Meanwhile, the company was still searching Tuesday afternoon for the exact cause of Monday's system outage.
|Have you received your AOL e-mail today? Add your comments to the bottom of this page.|
E-mail still down?
While AOL officials said earlier that the network and its e-mail system were only down for a few hours, according to one user, the e-mail difficulties continued into Tuesday afternoon.
"I've been trying to get mail in for over a day now, only to be told that service is unavailable," the user said.
Also, attempts by ZDNN to send mail to AOL users' mailboxes were unsuccessful as of the early afternoon.
The system-wide outage was the first of its kind in more than a year, AOL officials told Reuters.
However, AOL -- the largest of the online services with 11 million users - has intermittently suffered other service glitches ranging from delays in accessing the service to inability to send and receive e-mail.
The service problems led AOL last year to agree to comply with the demands of 45 state attorneys general in a class-action lawsuit. Last week, a judge in Chicago approved a settlement in Illinois' lawsuit against the company.